Process and device for measuring vital fetal parameters during labor and delivery

ABSTRACT

A process for measuring vital, fetal parameters during parturition. It is essential in this process that the blood pressure of the fetus is discontinuously measured in the arterial system by carrying out the occlusion process using the annular uterine tissue and the presenting part of the fetus and a pressure sensor and a sensor sensing the blood flow characteristics.

FIELD OF THE INVENTION

The invention relates to a process and a device for measuring vitalfetal parameters during labor and delivery.

BACKGROUND OF THE INVENTION

So far, a device for carrying out the so-called cardiotocography (CTG)has mainly been used in practice in obstetrics.

The child's heart rate and the mother's labor are represented in tworecording tracks in a side-by-side relationship on a recording stripwith this device so that, e.g., a midwife can watch the parturition bymeans of these recordings.

However, the CTG process does not supply any direct parameters. Therecordings must rather be interpreted by the midwife who consults adoctor when she is in doubt.

It is the object of the invention to provide a process and a devicewhich supply absolute values of vital fetal parameters duringparturition so that midwives get measuring values with clear statements.

In order to attain this object the invention provides that the bloodpressure of the fetus is discontinuously measured in the arterial systemby carrying out the occlusion process by means of the annular uterinetissue and the presenting part of the fetus and a pressure sensor and asensor sensing the blood flow characteristics.

Thus, the invention uses the principle of occlusion measurement of theblood pressure.

Although this principle has been generally known for a long time,experts have not recognized that, due to a further development, thisprinciple can surprisingly also be used for an indirect measurement ofthe blood pressure of the fetus during parturition.

In the known occlusion process for the indirect and discontinuousmeasuring of the blood pressure of a person, a cuff is placed around theupper arm. The cuff is inflated sufficiently with an air pump at thebeginning of the measuring of blood pressure that all blood vesselscollapse under the pressure of the cuff and there is no longer any bloodflow. Then the air is slowly discharged from the cuff, the bloodpressure range being slowly swept. As soon as the cuff pressure hasslightly dropped below the systolic blood pressure, blood can again flowin the veins during the time of the highest arterial blood pressure ofthe systoles.

Since the veins are still largely compressed, a hissing noise isproduced in the veins beyond the cuff during the short moment duringwhich arterial blood flows into the arm, which can be auscultated bymeans of a stethoscope (Korotkow sounds).

The noise can also be detected, of course, by a microphone and can beevaluated, e.g., electronically.

During the further course of the measuring, the cuff pressure iscontinuously lowered. Korotkow sounds get louder and louder, but thensofter gain. If the cuff pressure drops finally below the diastolicblood pressure, Korotkow sounds disappear completely.

The cuff pressure at which this noise occurs for the first timecorresponds to the systolic blood pressure. The cuff pressure at whichthis noise disappears finally or clearly decreases in terms of intensitycorresponds to the diastolic blood pressure.

SUMMARY OF THE INVENTION

In the process according to the invention the annular uterine tissue isdirectly or indirectly used for occlusion measuring in a surprisingmanner.

The process according to the invention is designed so that the annularuterine tissue is used as an occlusion cuff with respect to thepresenting part of the infant during the maximum of a contraction (peakof contraction), the occlusion pressure (pressure in the cuff higherthan the systolic arterial blood pressure of the fetus) between theuterine tissue and the presenting part of the infant being ascertainedby a pressure sensor and a sensor sensing the blood flowcharacteristics, the systolic and the diastolic arterial blood pressureof the infant being determined as the contraction subsides.

If the contraction is strong enough, the blood flow is completely cutoff in the relevant part of the fetus during the peak of a contraction.As the contraction subsides, the systolic and the diastolic bloodpressure of the fetus can then be determined successively.

If the labor is not that intensive, the midwife can cause the necessaryocclusion pressure by pressing on the abdomen or the uterus of themother. In many cases it may be sufficient to ask the mother to press bymeans of the abdominal muscles.

However, according to a further embodiment of the process according tothe invention, the uterine tissue can also be used by disposing anelastic hollow ring filled with a fluid between the uterine tissue andthe presenting part. The hollow ring is inflated until the occlusionpressure is reached, the systolic and the diastolic blood pressure ofthe infant being determined during the decrease of the pressure in thehollow ring by the pressure sensor and the sensor sensing the blood flowcharacteristics.

During a relatively mild labor, the hollow ring can be additionallyinflated in order to reach the necessary occlusion pressure so that theoccluding pressure reaches the systolic pressure of the fetus.

However, such a measuring of the fetal blood pressure in the arterialvascular system can also be carried out by the inflatable hollow ringindependently of the labor.

According to the invention, the fetal ECO can be derived from anelectrode attachable to the fetus. The obtained signals can alsofacilitate recognition of the blood flow characteristics.

The process of the invention can also be combined with the CTG processand/or the ECG process and/or the process of hemoglobinometry, i.e.,preferably with the process of pulse oximetry, but also with themeasuring of dyshemoglobins and the absolute hemoglobin value.

The process of the present invention can also include the step ofderiving the fetal ECG from a sensor such as the sensor sensing theblood flow characteristic or from the pressure sensor.

A device for carrying out the process is provided according to theinvention. The device carries out the occlusion process and consists ofa sensor disposed on the presenting part of the fetus, which senses theblood flow characteristics, and a pressure sensor disposed between theuterine tissue and the fetus.

Suitable sensors reacting to blood flow characteristics are known, e.g.,the corresponding sensors as parts of the devices according to EP 84 110306 or the international publication WO 90/01293 or DE-PS 38 10 008.

The device according to the present invention may further includeelectrical contacts for deriving the fetal ECG. The electrical contactsare provided on the blood flow sensor or the pressure sensor.

Doppler effect sensors or piezofoil sensors, for example, can also beused for this purpose.

The pressure sensor may consist of a hose filled with a fluid and closedat the front end, at whose rear end a pressure sensor element isdisposed.

However, the pressure sensor can also be designed as a balloon catheteror as an intrauterine pressure probe or as a double-recurrent ballooncatheter sensing both the occlusion pressure and simultaneously also theintrauterine pressure.

The device can also consist of a sensor disposed on the presenting partof the fetus and sensing the blood flow characteristics and of apressure sensor disposed between the annular uterine tissue and thepresenting part of the fetus, which is designed as an elastic,inflatable hollow ring filled with a fluid.

According to the invention, the hollow ring and the sensor sensing theblood flow characteristics can be fixed against each other as aconstructional unit.

In this fashion they cannot be displaced against each other, if, e.g.,the fetal head rotates away within the uterus after the application ofthe is arrangement.

BRIEF DESCRIPTION OF THE DRAWING

Further features and advantages of the invention will be understood fromthe following description in connection with the drawing, in which:

FIG. 1 & 1a show schematically a first example of a device for carryingout the process,

FIG. 2 shows another device of this kind,

FIG. 2a shows a detail of FIG. 2,

FIG. 3 shows another example of such a device,

FIG. 3a shows a detail of FIG. 3,

FIG. 4 shows another device of this kind,

FIG. 4a shows a detail of FIG. 4,

FIG. 5 shows still another example of such a device,

FIG. 5a shows a detail of FIG. 5, and

FIG. 5b shows a further detail of FIG. 5a.

FIGS. 3a, 4a, 5a and, 5b are drawn in enlarged scale.

DETAILED DESCRIPTION OF THE INVENTION

The uterine tissue, called cervical os in the following for the sake ofsimplification, is designated with 1 in the examples of embodiments andthe vagina is designated with 1a.

During parturition the fetal head 2 is pressed against the cervical os1.

An element 3 is affixed to the fetal head 2 through the vagina 1a, whichis a part of the blood flow sensor 4 sensing fetal blood flowcharacteristics. The element can be a spiral already used for thispurpose, but also a known piezofoil.

The blood flow sensor 4 supplies corresponding signals to an evaluatingunit (not shown).

In order to be able to detect the pressure prevailing between thecervical os and having an occluding effect, a further device is stillprovided.

This device is represented by a hose 5 in the example according to FIG.1, which is inserted between the cervical os 1 and the head 2 of thechild.

The hose 5 is closed at the front end and filled with a fluid whichtransmits the pressure to be measured to the rear end of the hose 5, towhich a pressure sensor element is affixed.

In the example according to FIG. 2, a balloon catheter 6 is introducedinto the occlusion zone as a sensor for sensing the occlusion pressure.

A further possible embodiment of the sensor for occlusion pressuresensing is the use of an already clinically introduced intrauterinepressure probe 7. Any differences between the intrauterine pressure andthe occlusion pressure can be balanced via a conversion factor (FIG. 3).

According to FIG. 3a, openings 7a are provided on the circumference atthe catheter tip of the intrauterine pressure probe.

A sensor for sensing the occlusion pressure is designed as adouble-recurrent balloon catheter 8. (The hose of the catheter has twoseparate channels or lumina, the one channel being connected to theballoon of the catheter, the other one to the catheter tip). The ballooncatheter can be used both for occlusion pressure detection and for thesimultaneous measuring of the intrauterine pressure.

Such a double-recurrent balloon catheter with openings laterallydisposed on the catheter tip is schematically shown in FIG. 4a. If thefetal blood pressure is to be measured in the arterial vascular systemin the case of relatively mild contractions or between contractions, thedevice according to FIG. 5 can achieve this purpose in order to alsoreach a sufficient occlusion pressure.

For this purpose, an elastic hollow ring 9 filled with a fluid isinserted around the blood flow sensor element 3 between the head 2 ofthe fetus and the uterine tissue 1. The hollow ring 9 can be inflated bymeans of a hose 10, and the pressure prevailing in its interior can alsobe measured. Thus, the occlusion pressure can also be reached byadditionally inflating the hollow ring 9 in the case of a relativelymild contraction. A sufficient occlusion pressure can also be reachedbetween the contractions by means of the hollow ring 9. The hollow ring9 is flattened on one side, this side 11 being relatively hard andserves as a support with respect to the uterine tissue 1.

In the example according to FIG. 5b, the hollow ring 9 is mounted on aflat support ring 12, which is made of a sufficiently firm, but flexiblematerial and is supported on the uterine tissue 1. The support surfaceof the hollow ring 9 on the head 2 of the child is smaller than thesupport surface of the support ring 12.

Thus, an increase in pressure can be achieved in a simple fashion. Thepresenting part of the fetus may not always be the head. The breech ofthe child can also be accommodated. The measurement of the fetal bloodpressure in the arterial vascular system is possible here, as well.

The hollow ring 9 and the support ring 12 can also extend to less than360 degrees.

The process can also be carried out prior to parturition, e.g., after apremature rupture and independently of labor.

The systolic and diastolic fetal blood pressure can also be measured inreverse order during the increase of a contraction. As a contractionsubsides, the measuring can be repeated in the customary order so thatmore accurate values are achieved (double determination).

We claim:
 1. A process for measuring the vital parameters of a fetusinside the uterus of a mother during labor and delivery, said processcomprising:forming an occlusion cuff about the presenting part of thefetus; disposing a blood flow sensor on the presenting part of thefetus; measuring the blood flow in the presenting part of the fetusthrough said blood flow sensor; disposing a pressure sensor between theannular uterine tissue and the presenting part of the fetus;discontinuously measuring the occlusion pressure between the annularuterine tissue and the presenting part of the fetus through saidpressure sensor; and determining the systolic and diastolic arterialblood pressure of the fetus.
 2. A process according to claim 1 includingmeasuring the occlusion pressure at the peak of a uterine contraction,and determining the systolic and the diastolic arterial blood pressureof the fetus as the contraction subsides.
 3. A process according toclaim 1 further comprising the step of determining the fetal ECG throughone of said blood flow sensor and said pressure sensor.
 4. A processaccording to claim 1 further comprising the step of simultaneouslymeasuring at least one of the fetal homoglobinometry, the fetal pulseoximetry, and the cardiotocography.
 5. A process according to claim 1further comprising the step of pressing on the uterus to enhance theforming of the occlusion cuff.
 6. A process according to claim 1 furthercomprising the step of having the mother press by using her abdominalmuscles to enhance the forming of the occlusion cuff.
 7. A processaccording to claim 1 wherein said pressure sensor is an elastic hollowring filled with fluid, the step of measuring the occlusion pressureincluding inflating said elastic hollow ring, and the step ofdetermining the systolic and diastolic arterial blood pressure of thefetus including decreasing the pressure in said elastic hollow ring. 8.A process according to claim 7 further comprising the step ofdetermining the fetal ECG through one of said blood flow sensor and saidpressure sensor.
 9. A process according to claim 7 further comprisingthe step of simultaneously measuring at least one of the fetalhomoglobinometry, the fetal pulse oximetry, and the cardiotocography.10. A device for measuring the vital parameters of a fetus inside theuterus of a mother during labor and delivery comprising:a blood flowsensor for placement on a presenting part of the fetus and adapted tomeasure the blood flow in a presenting part of the fetus; a pressuresensor for placement between annular uterine tissue and the presentingpart of the fetus and adapted to measure discontinuously an occlusionpressure between the annular uterine tissue and the presenting part ofthe fetus; and means for determining a systolic and diastolic pressureof the fetus based on the occlusion pressure.
 11. A device according toclaim 10 wherein said blood flow sensor and said pressure sensor arefixed against each other.
 12. A device according to claim 10 whereinsaid pressure sensor includes a hose having a closed front end and arear end, said hose filled with fluid, and a pressure sensor elementaffixed to said rear end of said hose.
 13. A device according to claim10 wherein said pressure sensor is a balloon catheter.
 14. A deviceaccording to claim 10 wherein said pressure sensor is an intrauterinepressure probe.
 15. A device according to claim 10 wherein said pressuresensor is a double-recurrent balloon catheter adapted to simultaneouslymeasure the occlusion pressure and the intrauterine pressure.
 16. Adevice according to claim 10 wherein said pressure sensor is an elastic,inflatable hollow ring filled with a fluid.
 17. A device according toclaim 16 further comprising an elastic support ring having a supportsurface for placement against the annular uterine tissue, said hollowring disposed on said elastic support ring and having a surface forplacement against the presenting part of the fetus which is smaller thansaid support surface of said elastic support ring.
 18. A deviceaccording to claim 16 wherein said blood flow sensor and said hollowring are fixed against each other.
 19. A device according to claim 16wherein said hollow ring has a first, flatted side for forming a supporton the annular uterine tissue.
 20. A device according to claim 19wherein said first, flattened side of said hollow ring is a rigidmaterial.
 21. A device according to claim 10 further comprisingelectrical contacts adapted to derive the fetal ECG, said electricalcontacts provided on one of said blood flow sensor and said pressuresensor.
 22. A device according to claim 10 wherein said blood flowsensor is a spiral.
 23. A device according to claim 10 wherein saidblood flow sensor is a piezofoil.
 24. A device for measuring the vitalparameters of a fetus inside the uterus of a mother during labor anddelivery comprising;a blood flow sensor for placement on a presentingpart of the fetus and adapted to measure blood flow in a presenting partof the fetus; pressure sensor means for placement between the annularuterine tissue and the presenting part of the fetus, the pressure sensormeans for forming an annular occlusion on the presenting part of thefetus.
 25. A device according to claim 24, wherein the pressure sensormeans is an inflatable hollow ring.
 26. A device according to claim 25,wherein the inflatable hollow ring forms a circular shape having aninterior portion, and wherein the blood flow sensor is located withinthe interior portion.
 27. A device according to claim 25, wherein theblood flow sensor and the inflatable hollow ring are fixed against eachother.